STABLE ISOTOPE-DILUTION MASS-SPECTROMETRY FOR THE SIMULTANEOUS DETERMINATION OF CORTISOL, CORTISONE, PREDNISOLONE AND PREDNISONE IN PLASMA

A capillary gas chromatographic-mass spectrometric method for the simultaneous determination of cortisol, cortisone, prednisolone and prednisone in human plasma is described. [1,1,19,19,19-H-2(5)]Cortisol, [1,1,19,19,19-H-2(5)]Cortisone, [1,19,19,19-H-2(4)]prednisolone and [1,19,19,19-H-2(4)]prednisone were used as internal standards. Formation of the bismethylenedioxy-3-heptafluoro-n-butyryl (BMD-HFB) derivatives made possible the separation of the four corticosteroids with good gas chromatographic behaviour. The new double derivatization has been demonstrated to be of value for sensitive and selective quantification by this technique. Detection was performed by monitoring the molecular ion (M+) of the BMD-HFB derivatives for cortisone and prednisolone, the [M - 18]+ ion for cortisol, and the [M - 30]+ ion for prednisone. The method requires no complex corrections for contributions and provides good accuracy and precision.